Hydraulic transmission



Feb. 27, 1934. wl FERRIS 1 Re. 19,095

HDRAULIC TRANSMISSION origina'l Filed April 11. 1921 e sheets-sheet 1www, A @M1915 1 Feb. 27, 1934. W- FERRlS HYDRAULIC 1TRANSMISSIONOriginal Filed April ll. 1921 6 Sheets-Sheet 2 fihi? 6 Sheets-Sheet 3Original Filed April 1l. 1921 Feb. 27, 1934. wA FERRIS HYDRAULICTRANSMISSION Original Filed April 1l, 1921 6 Sheets-Sheet 4 GSS( kvm@ 6Sheets-Sheet 5 W. FERRIS HYDRAULIC TRANSMISSION Original Filed April 1l.1921 Feb. 27, 1934.

Feb. 27, .1934. w FERRIS Re. 19,095

HYDRAULI C TRANSMIS S ION Original Filed April 11. 1921 6 Sheets-Sheet 6Reiwed Feb. Z7, 1934 PATENT OFFICE HYDRAULIC TRANSMISSION Walter Ferris,Milwaukee, Wis.,

assigner to Oilgear Company, Milwaukee, Wis., a corporation of WisconsinOriginal No. 1,619,200,

dated March 1, 1927,

Serial No. 4611.184, April 11, 1921. Application for reissue September11, 1933. Serial No.

27 Claims.

This invention relates to variable speed hydraulic transmissions of thetype employed for operating the carriage of a machine tool at eitherrapid traverse speeds or at selective feeding speeds. I

The transmission to which the invention applies in particular isprovided with a. motor for operating the carriage, a feed pump forsupplying liquid to the motor to drive the same at predetermined feedingspeeds, an auxiliary pump for supplying liquid to the motor to drive thesame at rapid traverse speed, and valve means for controlling the motor.

The present invention has as an object to provide a hydraulictransmission in which anv auxiliary pump supplies liquid to the feedpump to keep the same flooded.

Another object is to provide a hydraulic transmission in which theentire volume of liquid discharged from the motor during feedingoperations is delivered direct to the feed pump.

Another object is to provide a hydraulic transmission in which theentire volume of liquid discharged from the motor during feedingoperations 3 is delivered direct to the feed pump and any deciency inthis volume of liquid is made up by liquid supplied by an auxiliarypump.

Another object is to provide a hydraulic transmission w'ith an auxiliarypump and with valve meansV for directing liquid from the auxiliary pumpinto either side of the hydraulic circuit to either increase the owtherein or to supercharge the feed pump.

Another object is to provide a hydraulic transmission in which avariable displacement pump and an auxiliary pump are arranged Within thesame casing.

Another object is to provide a hydraulic transmission in which a unitarycontrol is employed,

According to the invention in its general aspect and as ordinarilyembodied in practice, the transmission is provided with a hydraulicmotork for connection to the mechanism or machine to be driven, avariable displacement pump for delivering liquid to the motor to drivethe same at predetermined speeds, fluid channels connecting the pump andthe motor and forming therewith a hydraulic circuit, and an auxiliarypump for supplying liquid to the variable displacement pump to keep itooded.

According to the invention` in another aspect. the variable displacementpump and the motor are connected to each other by substantially closedfluid channels during feeding operations whereby the entire volume ofliquid discharged from the motor is delivered direct to the intake ofthe variable displacement pump.

According to the invention in another aspect, the transmission isprovided with a pump unit consisting of a variable displacement pump andan auxiliary pump which are arranged in the same casing.

According to the invention in another aspect, a a single control elementis employed for adjusting pump displacement and for operating a valvewhich controls the delivery of liquid to the motor.

According to the invention in another aspect, the transmission isprovided with a valve which connects the two sides of the hydrauliccircuit to each other when the variable displacement pump is at zerostroke.

'Ihe invention is exemplified by the hydraulic transmission illustratedin the accompanying drawings in which the views are as follows:

Fig. 1 is a central vertical section through a pump unit which forms apart of the transmssion. the view being taken substantially on the line1 1 of Fig. 2.

Fig. 2 is a top plan view of the pump unit.

Fig. 3 is a vertical section taken through the pump unit at right anglesto the line 1-1 of Fig; 2 and with certain parts shown in full.

Fig. 4 is a sectional plan view taken on the line 4-4 of Fig. 1. *l

Fig. 5 is a sectional plan view taken on the irregular line 5-5 of Fig.1 and showing the control valve in its neutral position.

Fig. 6 is a sectional plan view taken in the same plane as Fig. 5 butshowing the control valve in feed position.

' Fig. 7 is a view similar to Fig. 6 but showing the control valveturned to one of its two quick traverse positions, the other quicktraverse position being with the valve rotated through an anglel of 180from the position shown.

Fig. 8 is a schematic drawing showing the control valve and the strokechanging cam connected by gears to each other for simultaneousoperation.

Fig. 9 is a sectional plan view taken on the line 9 9 of Fig. 1.

Fig. 10 is a sectional plan View taken on the line 10-10 of Fig. 1. y.

Fig. 11 is a sectional plan view taken on the line 11-11 of Fig. 1.

Fig. 12 is a schematic drawing showing the transmission applied to alathe.

Fig. 13 is a schematic drawing showing characteristics of the hydrauliccircuit and the stroke changing cam.

Fig. 14 is a diagram showing a modified form of stroke changing cam.

The transmission, for the purpose of explanation, may be dividedaccording to function into the following parts:A

1. A pump housing which encloses the principal working parts and servesas a reservoir for the motive liquid.

2. A variable displacement pump.

3. A constant displacement pump.

' 4. A hydraulic circuit including a control valve for controlling pumpdelivery.

5. Control mechanism for adjusting the variable displacement pump andfor operating the control valve.

1. The housing The housing comprises a lower combined supporting baseand oil sump A. It may be provided with supporting lugs A1. Above thebase is a middle section A2 bolted or otherwise fastened to the base.Across this middle section extends a deck A5. To the lower flange A4 ofsuch middle section is secured by suitable fastenings agear pump casingA5, which also serves as a support for the control valve. Upwardlyprojecting from the deck A3 is a hollow post A6 adapted to serve as apivot support for the variable delivery pump. A'I is a cover or topsection' bolted to the body A5 and A5 is a closure plate closing theupper end thereof.

2. The variable delivery pump The variable delivery pump comprises ashort stub shaft B munted in ball bearings B1 in the deck A5 and in thebushing B2 in the gear pump casing A5. B3 isv a spiral'gear keyed toits'shaft in mesh with another spiral Vgear B4 keyed to a horizontaldriving shaft B5 which shaft may be driven by any suitable source ofpower, preferably controlled by the spindle of the lathe or directlydriven from whatever source of power dri'es the'spindle so as to stopand start with thespindle. B5 is a driver or driving disc mounted on theupper end of the shaft B. This driving disc has on its upper face aplurality of outer lugs B" and inner opposed lugs B5. These lugs arestaggered and have opposed parallel surfaces. The outerr lugs B" havesecured to their inner surfaces roller paths or plates B'.

C is a hub rotatable on the .post A5 having projecting therefrom aswinging arm C1 ending in a hollow block C2 in which is rigidly mountedthe pintle C3. C4 is a cylinder barrel mounted for rotation on thepintle C3 inside the driver B5.

Projecting radially from this cylinder barrel are a series of cylindersC5 C5. Hollow plungers CE C5 are mounted for reciprocation within thesecylinders and contain push pins C7 C7 rigidly attached at their outerends to the crossheads C11 which are in slidable engagement with thesurface on the inner lugs Ba and on their outer sides engage rollers C9carried by the roller cage C1, the rollers being in engagement also withthe inner surfaces of the roller plates B9. The push pins extend throughthe crossheads to engage and limit the movement of the roller cages withrespect to the crossheads as indicated in Fig. 11, the roller cage beingslotted as at C11, so that any overtraveling of the roller cage ineither direction brings the end of the slot into engagement with theprojecting end of the push pin.

The oil or other hydraulic fluid is conducted to and discharged from thevariable delivery pump through the ilexible conduits D D1', whichconduits may serve interchangeably depending on the direction ofoperation of the pump as high pressure or low pressure passages. Theseflexible conduits terminate in fixed couplings D2 D5 at one end andcommunicate with the hollow head C2 and so with the pintle at the otherend. The pintle is provided with two separate ducts D4 D5 extendinglongitudinally therethrough and these ducts communicate with ports D5 D7in the face of the pintle registering with the ports D5 at the bottomsof the cylinders.

The ports D8 are reduced so that there is a hydraulic component tendingto move each cylinder on the pressure side inwardly toward the center.This hydraulic component tends to balance the wedging component of theliquid tending tofleak out between the pintle and the cylinder barreland to force the cylinder barrel away from center in the direction ofthe pressure side. The operation of the pump will be obvious from thedrawings. The cylinder barrel is eccentric with respect to the driverand as the two rotate in unison the plungers have a reciprocating motionin the cylinders. The plunger on one side of the pintle moves outwardlythrough substantially an entire half circle drawing working fluidthrough the low pressure ports into each successive cylinder, and aseach successive cylinder and plunger moves past the dead center, thesuccessive plungers commence to move in and expel the working fluid athigh pressure through the high pressure port. 1

Here it must be understood that if the eccentricity of the driver withrespect to the pintle be reversed, what were high pressure out-goingports become the low pressure incoming ports and what were the l'owpressure incoming ports become the high pressure out-going ports.

3. The constant delivery pump E is a horizontal pump drive shaft mountedin a ball bearing E1, the bearing itself being held in position by agland E2 in the wall of the body A2,

the inner race of the bearing being held in position on the shaft bymeans of the nut E3 screw threaded on the shaft. 'The shaft is driven byany suitable source of power not here shown. The inner portion of theshaft is rotatably mounted in a bearing E* supported on the deck A3 andcarries a mitre gear E5 in mesh with a mitre gear E' on the pump shaftE't which shaft projects upwardly out of the gear pump casing A5. Keyedon the shaft E'I is a pump gear E5 located within the gear casing and inmesh with a similar gear 1i'.11 keyed to the shaft E10. These two pumpgears lthe arrows on Figure l0.

4. Hydraulic circuit F is a supply or make-up passage in the cover E12and submerged beneath the level vof the oil or liquid in the reservoiror housing A. This make-up passage is in the form of a groove in theinner face of the cover and has an inwardly extending leg F1 terminatingbeneath the passage F2 which extends upwardly to discharge into theintake side of the pump chamber E11. The oil which is forced through thegear pump by the teeth is discharged from the pressure side into thevertical passage F3 which extends both above and below the pump chamber.The lower end of the passage F3 discharges into the passage F4 whichterminates at the inner end of the leg F1 of the make-up groove in thecover and is closed by a ball check valve F5 seated by the spring F5whose tension may be regulated by the screw plug F", F8 being a rotatingand' guiding pin on the screw plug, the purpose of this arrangementbeing to permit the liquid forced by the pump to short-circuit and bedis'- charged through the high pressure relief valve when the pressurein the balance of the system exceeds a predetermined maximum.

G is the distribution valve housing supported by and downwardlydepending from the deck A3 and formed integrally with the gear pumphousing A5. G1 is the distribution valve seat contained within thehousing G and provided with various ports as will hereafter appear. G2is a passage communicating at one end with the upper end of the passageF3 and having branches G5 and G'1 communicating respectively with portsG5 and G6 in the distribution valve seat G1 as shown in Fig. 4 which isa section along the line 4 4 of Fig. l.

The distribution valve which is rotatably mounted in the valve seat G1comprises an upper cylindrical head H seated upon the seat all the wayaround and a lower cylindrical head H1 seated upon the seat all the wayaround and joined by a web H2 of irregular cross section, bothcylindrical heads and the edges of the connecting web being closely ttedwithin the bore of the casing of the seat G1. 'I'his web is so arrangedand positioned as to provide on the left hand side as shown in Figure 1,a valve chamber H3 extending through an angle of about 120 degreesand-adapted to bein register with the port G5 through a wide range ofrotation of the valve. H4 is a duct leading from the chamber H3downwardly through the valve head H1. This duct is closed at its lowerend by a low pressure relief valve H5 seated by the spring H5. Thisconduit H4 discharges into an annular chamber H7 formed between the gearchamber cover E12 and the `lower end of the valve, the valve beingsupported on the cover for this purpose by the lug H5. H9 is a passagein the `face of the gear casing cover communicating at one end with theannular chamber H'l and at the other end with the make up passage F andthe leg F1. The passages just described are those which permitcirculation of oil by the gear pump when no useful work is beingaccomplished with the exception of replacing leakage and maintaining theinitial pressure to prevent the formation of vacuum and air pockets.This causes the gear pump to replace leakage and maintain saidcirculation with a minimum expenditure of power. H10 is a branchextending upwardly from the chamber H3 and adapted to registerselectively with the ports I4 and I5, the branches I11 and H1o beingadapted to be in communication respectively with one or other of theopposed ports I4 and I5 when the controller lever is at one or other ofthe degree positions for quick traverse.

I and I1 are distribution mains communicating with the couplings D2 D3and therefore, in series with the adjustable feed pump through thepassages D,l D5, D4, D1. I2 I3 are branches extending inwardly from themains I I1 and registering with the ports I4 I5 in the valve seat G1,which two ports may be in register with a transverse by-pass passage I5formed in the valve web H2. At either end of the by-pass passage I6 areangularly extended pockets 116 I25 in the periphery of the valve bodyfor the purpose of permitting a considerable angular movement of thevalve before interrupting the return of the make up uid through theby-pass passage to the low pressure side of the system. I7 is a chamberformed in the valve body in register with the port G5 and extendingthrough such an angle that the port and chamber are in register at allangular positions of the valve. Ia is a branch extending upwardly fromthis chamber and adapted to communicate with either of the two ports I4I5 through the make up opening I9 and by-pass passage I6. This branch I8is also adapted selectively to be brought into direct register with theports I5 or I4 when the =,valve is rotated from the position shown forinstance in Fig. 5 to the position shown in Fig. 7, thereby throwing theentire discharge of the gear pump selectively into either port. It willthus be seen that when the distribution valve is in position shown inFigure 5, the discharge of the gear pump is in communication, throughbranch I5, make up opening I9, by-pass lI6 with both ports I4 and I5,and is hence in position to replace leakage occurring anywhere in thesystem. With the distribution valve in the position shown in Figure 6 orin the symmetrical position on the v other side of the center line fromthe position shown in Figure 6, the gear pump dischargeA is cut off fromport I1 or port I5 respectively but remains so positioned as to make upleakage occurring from those parts of the system which are incommunication with port I5 or port I4 respectively which as willhereinafter appear, is the low pressure side of the system, this make upcoming through the branch I8, make up opening I9, by-pass I5, and pocket115 or 123 to ports I4 or I5 as the case may be, the pockets permittingthis to continue' even after the valve has rotated far enoughto bringthe by-pass passage with the pockets out of line with the ports.

The mains I I1 communicate with opposed ends of the motor cylinder K.For the purpose of illustration I have shown this motor cylinder K witha. piston K1 driving a piston rod K2 which in turn propels a toolcarriage K3 on a lathe bed K4, though of course, any desired tool orapparatus might be operated by this motor. In

the operation of any such device as this, therewill always'be someimmovable -obstacle or stop at which the motor parts may come to rest.This might for instance be the ends of the cylinder.

In many machine tools such a stop would be inusov `est

the carriage and adapted to travel along an adjusting screwKG. K1 and K3are stop nuts positioned on this screw and adapted to be set in positionby the operator to limit movement of the carriage by engagement with thelug K5. When the tool carriage or whatever part is being drivenl by myapparatus comes to the end of its travel, the motor ceases to functionbut the pump will keep right on building up pressure and in order thatno harm may be done by this, I provide a by-pass pipe K9 extendingacross between the mains I I1 and located in parallel with the motorbetween the two mains. Thisfby-pass pipe or line is associated with somekind of a pressure relief valve. In the preferred form, I have shown thepressure relief valves .K10 K11 associated with the mains I I1, thevalve K1? being adapted to open under excessive pressure in the main I,the valve K11 being adapted to open under excessive pressure in the mainI1, each of these relief valves being adapted' to permitunobstructedflow of fluid in the direction opposite to its pressurereleasing direction.

vTheY purpose of having two separate valves instead of a single reliefvalve adapted to open in both directions or a double acting valve isthat it may be possible to separately set these valves to release underdiiferent pressures becau:e under ordinary conditions, it is desirableto have different maximums for forward movement and reverse.

The description of one of these pressure relief valves will suffice forboth. M is the valve housing. The main I1 communicates with the valve atone end and the bypass pipe K9 at one side of the housing. M1 is ahollowplunger slidably mounted in the neck of the valve. This plunger isenlarged at its end as at M2 and held upon a seat around the valve neckby means of the spring M3, the compression of this spring beingadjustable by means of a plunger M4 screw threaded in the valve body andadapted to be rotated to tighten or loosen the spring by the handle M5.M6 M1i are ports in the wall of the hollow plunger closed while theplunger is in its normal seated position, but adapted to be opened aftera sufficient movement of the plunger in the direction opposed to thepressure exerted.

by the spring so as to permit the l`quidl to flow out throughthe plungerand the ports when the pressure is great enough to compress the spring.Ml is a passage through the end of the plunger closed by a ball checkvalve M11 against fluid attempting to pass in the direction opposed tothe spring pressure. The lift of the ball is limited by the pin M9, whenthe liquid flow takes piace in the opposite direction.

5. The control mechanism O is the distributing valve stern. It is pinnedat its lower end to the valve body penetrating within the head Hlthereofand passes up through the hollow post A and through the hub O1 whichgives it a bearing at the top of the housing. O2 is a lever keyed to thevalve stem and having a manipulatng handle O3 and a pointer O* adaptedto travel along the graduated limb O5 mounted on the housing. OE is agear keyed on the valve stem inside the housing. This gear1 is in meshwith an idler O7 mounted on the pin Oa on the swinging lever C1. O9 is apinion in mesh with the idler O" and mounted for rotation on a pin O111projecting upwardly from the pintle C3.

l is a cam preferably integral with or at least rigidly mounted in thehub of the pinion 0 and having its working face in engagement with aroller P1 which is mounted in an abutment or lug P11 extending inwardlyfrom the wall of the housing A". P11 is a spring interposed between theswinging arm and the housing wall adapted to hold the cam and rollerrmly in working engagement one with another. 'I'he neutral, central orintermediate portion ofthe cam between the points Pi1 P4 is circular sothat rotation of the cam through an angle of 17 degrees each way fromthe central position does not result in any swinging of the arm C2. Thecam radii are progressively greater than the radius of the arc` P3 P4 inone angular direction from the central point and progressively less inthe opposite direction. Rotation of the cam in one direction moves theswinging arm in a clockwise direction while a reverse rotation of thecam moves the swinging arm in the opposite direction and since thepintle of the variable stroke pump is mounted on the swinging arm,movement of the cam results in relative displacement of axes of rotationof the driver and cylinder barrel in one direction for forward movementand in the other direction for reverse. These two cam surfaces extendapproximately 72 degrees away from the end of the central circularportion to the points P5 P6, and from these points on to P'1 P8 forabout 35 degrees, the cam is again at both ends circular. The reason forthis arrangement is that it is necessary as the lever commences torotate, for the distribution valve to have suicient annular ymovement toclose off the bypass I6 at the beginning of the working cycle, then asthe cam rotates, the pump is thrown into operation by displacement ofthe pintle axis and this displacement continues in one direction or theother until maximum stroke of the pump has been reached at about 90degrees each way from zero position of cam P. But this does not givemaximum feed because for quick traverse, I Want to add to the fluiddisplaced by the variable displacement pump the relatively greateramount of fluid displaced by the gear pump and this must be done withoutinterfering with the .continued operation of the variable pump. As thecam continues its rotation beyond the points P5 or P6, no further changein axial relations takes place because the cam is now circular, butduring this period, the lever continues to rotate the distribution valveto throw the full displacement of the gear pump into the 'high pressuremain and to add it to the displacement of the adjustable pump so as togive the maximum volume of working fluid and consequent maximum speed`of rapid-traverse.

General S is a shaft driven from the lathe head stock. It carries thepulley S1 which drives the belt "El2 travelling around the pulley S3 onthe shaft B5, so that in the apparatus I have used to illustrate myinvention, the variable pump driving shaft is driven only when the lathespindle or head stock is driven.

The make-up circuit is normally a. separate circuit through which themake-up liquid is circulated under low or make-up pressure by the gearpump. The Working circuit, containing as it does a high and low pressurebranch, a motor and a variable displacement pump, is also normally aseparate circuit. The only connection between these two circuits whenfeeding is going on is through the make-up passage in the valve, and aslong as leakage is taking place there will be a ow through this passagefrom the make-up circuit into the low pressure side of the workingcircuit. However, when the motor is moving back so that the piston rodis coming into the system, the displacement of the piston rod Visgreater than any possible leakage, and therefore the volume of liquidwhich can be maintained in the system decreases and this results inforcing liquid out against the normal make-up ow back into the make-upsystem and thence through the low pressure or make-up pressure reliefvalve in the reservoir.

In the mechanism described, the make-up circuit, including the gear pumpand low pressure relief valve, thus serves not only to replenish theWorking circuit with oil to compensate for leakage losses but also tomaintain the working circuit flooded during variations in volumetriccapacity therein caused by movement of the piston rod inwardly andoutwardly of the left end of the power cylinder. As the piston rod movesinto the left end of the cylinder, oil is forced out of the return sideof the working circuit through the low pressure relief valve and, asthis rod moves out of the cylinder, a fresh body of oil from thegearpump is forced into the return side of the working circuit tocompensate for this increase in volumetric capacity in the circuit. Thisrepeated action of forcing oil from the circuit during decrease involumetric capacity of the circuit and returning fresh oil to thecircuit during increase of capacity thereof tends to keep the circuitfree from entrained air. Furthermore the fact that theY return side ofthe circuit is always flooded with oil under pressure insures promptaction of'the piston upon each reversal of flow in the circuit.

It willl be noted that adjustment of the ccntrol lever O2 through anangle of approximately sixty degrees in either direction from theneutral position of Figure 2, effects a corresponding angular adjustmentof the distribution valve, and a simultaneous adjustment of the controlcam P through an angle of approximately ninety degrees in eitherdirection from the neutral position of Figure 8. In all positions of thevalve, within this range, the chamber H3 thereof is open to the port G5,so that passage IH*1 is open to the gear pump through passage G4 and thepressure in the gear pump circuit `is thus determined by the lowpressure relief valve H5. During clockwise adjustment of the lever O2from neutral into this sixty degree position, branch 125 of the valve isopen to port I5, so that pipe I1 is open to the gear pump throughpassage G3, chamber I7, passage IB and pipe I5; and the high portion ofthe cam P (between points P4 and P5) bears upon the roller P1, so thatthe variable displacement pump delivers liquid through pipes D and I andliquid returns to the variable displacement pump through pipes I1 andD1. During counter-clockwise adjustment of the lever O2 from neutralinto the sixty degree position branch. I15 is open to port I4, so thatpipe I is open to the gear pump; and the low portion of cam P (betweenpoints P3 and P5) bears upon roller P1. so that the variabledisplacement pump delivers into pipes D1 and I1, and pipes D and I thenconstitute the return side of the circuit. Thus during adjustment of thecontrol lever O2 between these sixty degree limits, the displacement ofthe Ivariable displacement pump is adjusted from zero to a maximum ineither direction, and in all positions of the lever between thesepositions the gear pump is connected to the return side of the circuitand maintains the same flooded with liquid `under pressure, the degreeof pressure therein being determined by the valve H5. The gear pump isthus connected in serieswith the variable displacement pump.` I Themaximum pressure in the working side of the main circuit is determinedby the high pressure relief valves K10 or K11.

Adjustment of the lever O2 clockwise thru anv angle of ninety degreesfrom neutral, turns the distribution valve through a corresponding angleinto the position of Figure '7, in which position chamber H3 is openedto port I5 through passage H1", and chamber IFI is opened to both portsG5 and G5 and to port I through passage I5. Cam P is simultaneouslyadjusted so that roller P1 engages the circular portion Pi-P8 of the camand the variable displacement pump delivers liquid through pipes D andI, liquid returning to this pump through pipes I1 and D1. In thisposition of the valve iluid from the gear pump is delivered frompassages G3 and G4, through chamber I7, port I1 and pipe I2 into pipes Dand I, so that this fluid is added to the fluid discharged by thevariable displacement pump, to increase the flow in the circuit. Thegear pump is thus connected in parallel with the variable displacementpump. With the parts in this position any excess liquid within thereturn side Il---D1 o1' the main circuit is discharged through pipe I3,port I5, passage H10, chamber H3, and passage H4 past the low pressurevalve H5. Under this condition the highest pressure obtainable withinthe working side of the circuit is determined by the valve F5 whichdetermines the maximum gear pump pressure. With the handle O2 adjustedinto the opposite ninety degree position, the discharge from thevariable displacement pump is reversed, so that pipes I1 and Dl becomethe working side and pipes I and D the return side of the circuit, andthe valve connections are reversed so that the entire discharge of thegear pump is delivered through pipe I into the working side of thecircuit.

Experience shows, however, that under this 120 condition it may happenthat while the large capacity pump is diverted from its make-up functionthe pressure on the low pressure side will drop below the pointnecessary to keep the pistons in the variable displacement pump tight,125 and this results in rattling and irregular operation of the variabledisplacement pump; and so for many conditions it is desirable to use acontrol cam so arranged that at the end of the movement, when thevariable displacement pump 130 reaches its maximum, the pump issuddenly, by further movement of the control lever, thrown back to thezero position, and under this condition the make-up pump alonecirculates the hydraulic fluid for quick traverse. i

An arrangement for this purpose is shown' in Fig. 14, wherein the cam Yis substituted for the cam P, and this cam has a neutral or circularsurface Y1, with cam surfaces Y2, Y3 adapted to control and vary theeccentricity of the pump 140 and sudden sharp return surfaces Yi, Y5leading to a cylindrical surface Y6A having the same radius as Y1, sothat at both ends of its movement the controller lever causes thedisplacement of the variable displacement pump to re- ,145 turn to Zero.

In order to insure the return oi' the feed pump stroke to a positionwhere the inner ends of the plungers will be subjected to the 'deliverypresvhave found it advisable in some cases to make the cam surfaces Y'not truly circular as above described, but to form the surface at Y16with a radius slightly less than Y1 so that the roller on leaving thehigh surface Y3 will pass to a position which will slightly reverse thefeed pump, instead of attempting to return it exactly to zero position.For the same reason the surface at Y2E may be formed with a radiusslightly greater than the radius at Y1. l

It will be noted that when the distribution valve is in the intermediateposition of Figure 5 the passage I5 is open to both ports I4 and I5, sothat pipes I and I1 communicate therethrough. The pump circuit,including pipes D and D1, is thus by-passed, and the opposite ends ofthe power cylinder K are also in open communication. The piston K1 isthus free to move lengthwise of the cylinder permitting the operator tomove the tool carriage K3 by hand along the bed of the lathe.

Operation A description of the operation of the machine will now begiven. Let it be assumed that the entire system has been filled with oilin the usual manner; that the motor E13 has been started so that theshaft E and gear pump are rotating at constant speed; that the lathespindle S has been started so that the variable displacement pump isrotating at a corresponding, substantially constant speed; that the toolcarriage K3 and pistonl K1 are in the positions of Figure 12; and thatthe control lever O3, distribution valve and cam P are in the positionsindicated in Figures 2, 4, 5 and 8. vWith the valve and cam in thisposition, the two sides of the circuit are in open conimunicationthrough pipe I3 port I5, passage I6, port I4 and pipe I2, and thevariable displacement pump is in zero displacement position, so thatpiston K1 and the tool carriage K3 are at rest. It will also be notedthat the gear pump is connected to both sides of the circuit throughpassage G3, port G5, chamber I1, and passages I3, I9 and IG, and alsoconnected through passage G4, port GG, chamber H3 and passage H4 leadingto the low pressure relief valve H. Both sides of the circuit are thusmaintained flooded with liquid, at a low pressure determined by thevalve H5, the excess liquid discharge past this valve returning to thegear pump through passages H9, F, F1 and F3.

When the operator wants to start up the feed, he moves the controllerhandle to the right or left as the case may be. In Figure 13, I haveshown the effect of moving it in a clockwise direction. The rlrst thingthat happens is that the distribution valve rotates and the by-passpassage I6 is thrown out of register with the port I4.

This closes and interrupts the short circuit between the mains I, I1.The rotation of the controller lever also rotates the train of gears atthe top of the housing and rotates the controller cam. Since the centralportion of this cam is cylindrical, the cam can rotate until the pointP4 passes the line joining the center of the cam P and the roller P1without causing any angular rotation of the swinging arm, the arm beingfirmly held against the abutment by the spring. This rotation of the camand controller lever is sufcient to completely close the by-pass. therrotation of the controller lever, however,

brings that part of the cam having the progressively increasing radiusinto contact with the roller.

As shown in Figure 13, this rotation has continued until the rollerengages the cam about onehalf way between points P4 and P5 so that theswinging arm and pintle block are forced to one side to bring theeccentricity of the pintle With respect to the driver about one-half Waybetween maximum and zero.

The variable displacement pump rotates in the direction of the arrows inFigure 11 counterclockwise, and the result of this is that the righthand side of the variable delivery pump is the high pressure side andworking uid is discharged through the ports D8 from the cylinders intothe port D7, thence through the passages D5 and D, through the couplingD2 to the passage I and thence to the head end of the motor K tending toforce the piston K1 toward the other end of the cylinder. Because theby-pass I5 is out of register with the port I4 and therefore closed andbecause the check valve K1o is seated, all of the Working iluiddisplaced by the variable delivery pump is employed in moving the pistonK1. 'I'he Working fluid on the other side of the piston' K1 travels fromthe cylinder K through the main I1, the coupling D3, the ilexible tubeD1, the passage D4 and the low pressure port D6 into the varioussuccessive cylinders on the low pressure side of the variable deliverypump, thence being carried around and discharged on the high pressureside as the cylinders continue their rotation.

While this goes on, a certain amount of working iluid may have leakedout of the high pressure system between the working surfaces or The makesages F3, G2, G4, port G5, chamber H3, passage H4 past the valve H5through the annular chamber H'1 into the passage H9 and thence throughthe passage F, F1, F2 back to the intake side of the gear pump. If thereis any leakage however to be made up, the make up material will leavethe passage G2, travel through the passage G3, port G5 to the chamber1'1, thence through the branch I3 make up port I3, by-pass passage I5,pocket 135, port I5 and passage I3 to discharge into the low pressuresystem or side at the coupling D3. This will withdraw some of the gearpump discharge and in order to make it up, exactly the same amount ofmaterial that has leaked out and been replaced will be drawn into thegear pump system from the reservoir through the right hand end of thepassage F. In order to work in the opposite direction, the operatormerely swings the controller lever in the reverse direction and thiswill bring that part of the cam between the points P3 and P5 intoengagement with the roller and will reverse the direction ofeccentricity of the driver and cylinder barrel. When this is done,although the driver rotates in the same direction, what was the lowpressure becomes the high pressure side of the system and vice versa,the pump then discharging its high pressure through the passages D4 D1and I1 to the piston rod end of the motor. Simultaneously thedistribution lvalve will have been rotated in the opposite direcwill beno connection between the high pressure side and the make up because thepocket 125 and passage I5 willbe out of register with the port I5. Thedirection of travel of the make up fluid, however, will remain constantin the gear pump system because the gear pump always rotates in the samedirection, the distribution valve always functioning to conduct the makeup fluid to the low pressure side of the system whichever that may be.

The rate of feed or travel provided by the variable delivery pump iscomparatively slow and susceptible of exceedingly accurate adjustment,since the control lever has a relatively Wide range of travel and therelation between rate of feed and position of control lever isexceedingly accurate and delicate. It frequently is highly desirablehowever to provide a quick traverse feed which needs to be much morerapid but does not need to be so accurately timed and controlled as theworking feed or speed provided by the variable displacement pump. I'hisquick traverse can be obtained by rotating the controller'lever to the90 degree position in either direction. When this is done, the extremecircular terminal face of the cam either on one side or the other, comesin contact with the roller at the end of the increasing or decreasingcam segment and there will at that point be no further angulardisplacement of the swinging arm and no further change in theeccentricity of the driver and cylinder barrel. But the further rotationof the controller handle shown ,for instance at the place at which P5comes in contact with the roller, will cause a further rotation of thedistribution valve to the position shown in Figure 7, at which positionthe working fluid discharged by the gear pump passes along the passageG2, divides and part of it comes through the passage G3 and part throughthe passage GL1 into the chamber Il, thence up through the branch I8discharging through the port I4 and passage I2 into the high pressureside of the system. This relatively large quantity of working fluidgreatly accelerates the travel of the piston or motor because the volumedisplaced by the gear pump is much greater than the volume displaced bythe variable delivery pump and in this case the two volumes are added toeach other to produce increased speed or rate of displacement, thisresulting in quick traverse of the machine or lathe carriage. Theworking fluid from the low pressure side of the motor is returned to thehigh pressure side partly by the variable delivery pump and partly bythe gear pump. The working fluid handled by the gear pump passes fromthe main I1 in Figure 13 through the coupling D3, passage I3 port I5.branch H15, chamber H3, duct H4, unseats the valve H5, passes throughthe chamber H7, passage H9, passage F, passages F1 and F2 to the lowpressure or intake side of the gear pump.

If quick -traverse in the opposite'direction were being provided, thecontroller lever would be rotated in the opposite direction 90 degreesfrom the neutral position shown in Figure '7 and in this case, the pathof the,discharge from the gear pump would be exactly the same up to thedistribution valve, but would thence be through the port I5, passage I3,coupling D3, to the main I1 which would under these conditions be thehigh pressure main and the working fluid would be returned to the lowpressure side of the two pumps through the main I, part going to thevariable displacement pump through the conduit D and part to the gearpump through the conduit I2, port I4,

through the distribution valve and back to the gear pump as aboveexplained.

The system is adapted to work under various conditions under threedifferent operating pressures each of them limited by a separatepressure relief valve and the system is so arranged that each separatepressure relief valve is only operative in the circuit when it isdesired that it shall function.

There is rst the make up relief valve. This is the valve H5 located atthe bottom of the distribution valve and set so that with the frictionalresistance to the movement of the Working fluid in the system, therewill always be a minimum pressure of about fteen pounds. Under someconditions, thisvalve might be altogether omitted, the frictionalresistance of the passages to the flow furnishing sufficient make uppressure. All that is necessary is that there be enough pressure toinsure the penetration of the make up supply of the working fluid intothe low pressure side of the system to compensate for all leakage whenuseful work is being done and into both sides when the machine isidling.

The next higher pressure involved is xed by the quick traverse reliefvalve F5 shown in Figure 9. When pressure on the high pressure side ofthe system with the controller valve in one or other of the 90 degreeangles for quick traverse, exceeds a certain higher maximum, thepressure will unseat the valve F5 and permit the working fluiddischarged by the gear pump to pass in through the complete system,l butto short circuit from the lower end of the passage F3 through theby-pass passage FA1 back to the valve end F5 which it unseats thenceinto the passage F1 up to the passage F2 to the lower pressure or intakeside of the gear pump. This can only take place when the parts are inthe position shown in Figure '1 or in the opposite 99 degree positionand under such conditions as this, the make up relief valve H5 has noeffect because it is on the return or low pressure side and it continuesthe function of keeping the pressure on the low pressure branch of thegear pump circuit up to such point at which make up will take place, anddoes not in any way affect the operation of the quick traverse reliefvalve.

When the distribution valve is in the range of feeding positions asexemplified in Figures 6 and 13,-and especially the working positionshown in Figure 13, there is no direct communication between the gearpump discharge and the high pressure side and therefore the gear pumppressure relief valve has no effect on the pressure in the high pressurecircuit and the pressures may rise above the pressures at which thequick traverse pressure relief valve would operate. These higher feedingpressures are determined by one or more pressure relief valves.Preferably, each of the two pressure mains is provided with a reliefvalve in order to have different maximum pressures for feeds in oppositedirections; but for the purpose of comparison we can consider these twopressures as one because only one of these pressure relief valves canoperate at a time; the other having for the moment no working function.The tensions of these springs of these two valves K1 K11 c'an beseparately ad- ,iusted and if I is the high pressure side, the valve K10will open and permit fiow of working uid through the by-pass K9 and thevalve K11 when a certain predetermined pressurehas been reached: and ifthe main I1 is the high pressure main, the valve K11 will open when acertain predetermined pressure has been reached to permit passage of theworking fluid through the by-pass K and the valve K1u into the-partwhich is then the low pressure main I.

l The invention is hereby claimed as follows:

l. In a hydraulic transmission the combination of a hydraulic motor, avariable displacement pump for delivering a driving liquid thereto,means for regulating pump displacement to regulate the speed of saidmotor within a limited range, a second pump for driving said motor,valve mechanism for controlling the discharge from said second pump toincrease the speed of said motor above said range, and a unitary meansor controlling said displacement regulating means and said valve.

2. In a hydraulic transmission the combination of a hydraulic motor, avariable displacement pump for driving said motor at a variable ratewithin a limited speed range, a second pump for increasing the speed ofsaid motor, a control element, means controlled by said element forregulating the displacement of said rst named pump, and means controlledby said element for, controlling the discharge from said second pump.

3. In a hydraulic transmission the combination of a hydraulic motor, avariable displacement pump, a. hydraulic circuit directly connectingsaid pump and motor through which said motor is normally driven at arate corresponding to pump displacement, means for regulating pump dis-lplacement, a second pump, a'nd means adjustable to selectively connectsaid second pump with either the Working side or the return side of saidcircuit. i

4. In a hydraulic transmission the combination of a hydraulic motor, areversible flow variable displacement pump for driving said motor at avariable speed in either direction, a second pump for driving said motorat an increased speed, valve mechanism for controlling communicationbetween said second named pump and motor, and unitary control means forvarying the displacement of said first named pump and for operating saidvalve mechanism.

5. In a hydraulic transmission the combination of a hydraulic motor, avariable displacement pump for delivering a. driving liquid to saidmotor, a second pump for delivering a driving liquid to said motor, acontrol element, means responsive to movementA of said element through alimited range for varying the displacement of said iirst named pump, andmeans responsive to movement of said element beyond said range forconnecting said second named pump in driving relation with said motor.

6. In a hydraulic transmission the combination of a hydraulic motor, a.reversible flow variable displacement pump for delivering a drivingliquid to said motor, a second pump for delivering a driving liquid tosaid motor, a control element movable from a neutral position into anextreme position in either direction, means responsive to movement ofsaid element for regulating Ithe displacement of said first named pumpand for reversing the flow thereof during movement of said elementthrough neutral position to vary the speed and reverse said motor, andmeans responsive to movement of said element into either extremeposition for connecting said second named pump in driving relation withsaid motor in either direction of operation thereof.

7. In a hydraulic transmission the combination of a hydraulic motor, avariable displacement pump for delivering a driving liquidvto saidmotor.

a second pump for delivering a driving liquid to said motor,displacement regulating means for said first named pump operable toregulate the flow therefrom, a valve mechanism for controlling the flowfrom said second named pump, and means for controlling said regulatingmeans and said valve mechanism.

8. In a hydraulic transmission the combination of a hydraulic motor, avariable displacement pump for driving said motor, cam mechanism forregulating pump displacement, a second pump for driving said motor,valve mechanism for controlling the discharge from said second pump, andmeans for controlling said valve and cam mechanism.

9. In a hydraulic transmission the combination of a hydraulic motor, avariable displacement pump, cam mechanism for regulating pumpdisplacement, a second pump, valve mechanism for controlling thedischarge from said second pump, and a single control element forcontrolling said cam and valve mechanism,

10. In a hydraulic transmission the combination of a closed hydrauliccircuit having working and return sides, a variable displacement pumpfor feeding said circuit, a second pump, and valve mechanism adjustableto deliver liquid from said second named pump into said return side tomaintain said circuit flooded or into said Working'side to increase theflow therein.

11. In a hydraulic transmission the combinau tion of a closed hydrauliccircuit having interchangeable Working and return sides, a reversibleflow variable displacement pump for feeding said circuit, a second pump,and valve mechanism adjustable to deliver liquid from said second pumpinto the return side to maintain said circuit flooded or into theworking side to increase the flow therein.

12. In a hydraulic transmission the combination of a hydraulic circuit,a variable displacement pump for feeding said circuit, means forregulating pump displacement, a second pump, and valve mechanismadjustable to connect the discharge side of said second named Vpump withthe discharge side of said first named pump to increase the flow in saidcircuit or to connect the discharge side of said second named. pump withthe intake side of said rst named pump to supply liquid under pressurethereto.

13. In a hydraulic transmission the combination of a closed hydrauliccircuit of varying volumetric capacity and having Working and returnsides, a. pump in said circuit, a second pump, means adjustable toconnect the discharge side of said second pump' either with return sideof said circuit to compensate for variations in the ycapacity thereoi orwith the working side of said circuit to increase the flow therein, anda relief valve cooperating with said second pump when the dischargethereof is connected with the return side of said circuit to maintainsaid return side flooded with liquid under pressure.

14. In a hydraulic transmission the combination of a reversible nowclosed hydraulic circuit of varying volumetric capacity havinginterchangeable working and return sides, a. reversible variabledisplacement pump in said circuit, a second pump, means adjustable toconnecttheV discharge from said second pump either y with the returnside or with the Working side of said circuit in either direction offlow therein, a low pressure relief valve cooperating with said secondpump when the discharge thereof is connected with the return side ofsaid circuit to maintain the return side of said circuit flooded withliquid under low pressure, and a high pressurerelief valve operable toprevent excessive pressures in the working side of said circuit.

15. In a hydraulic transmission the combination of a hydraulic motor, areversible flow hydraulic circuit for driving said motor havinginterchangeable working and return sides, a variable displacement pumpfor feeding said circuit, a second pump, valve mechanism adjustable toconnect the discharge of said second pump either with a return side or aworking side of said circuit in either direction of flow therein, a lowpressure relief valve cooperating with said second pump when thedischarge thereof is connected with a return side to maintain saidreturn side flooded with liquid under pressure, means for A regulatingthe displacement of said variable displacement pump, and a controlelement for controlling said valve mechanism and said displacementregulating means.

16. In a machine of the character described having a work holder, a toolcarrier, and means for effecting relative movement between said holderand carrier to effect a cut, the combination of a hydraulic circuitincluding a variable displacement pump driven by said means foreffecting a regulated feed movement between,

said holder and carrier during the cut, a second pump for effectingrapid movement between said holder and carrier for rapid traverse, andmeans for regulating the displacement of said rst named pump and forcontrolling the flow of liquid discharged from said second named pump.

17. In a machine of the character described having a work holder, a toolcarrier, and means for effecting relative rotation between said holderand carrier to effect a cut, the combination of a hydraulic circuitincluding a variable displacement pump for effecting a regulated feedmovement between said holder and carrier during the cut, a second pumpfor effecting rapid movement between said holder and carrier for rapidtraverse, a single control element, means controlled thereby for varyingand controlling the displacement of said first named pump, and Valvemeans controlled by said element for controlling the discharge from saidsecond named pump.

18. In a hydraulic transmission, the combination of a hydraulic motor, arapid traverse pump, a'hydraulic circuit including valve mechanismoperable to connect said pump with said motor to effect rapid traverseoperation thereof in either direction, a variable displacement feed ratepump connected to said motor for eifecting operation thereof at apredetermined feed rate, connections through which said feed rate pumpis suppliedv with liquid from said circuit to maintain said feed ratepump ooded under all conditions of operation, means for regulating thedisplacement of said feed rate pump, and means for operating said Valvemechanism.

19. The '.combination, with a machine tool having a movable member, of ahydraulic circuit including a hydraulic motor for moving said member atfeeding and rapid traverse rates and a variable displacement feed ratepump for metering the flow in said circuit to thereby accuratelyregulate the rate of movement of said member during feeding, a liquidreservoir, a second pump supplied from said reservoir and cooperatingwith said circuit to keep said feed rate pump flooded, and valve meansoperable to direct the discharge of said second pump into the workingside of said circuit` to increase the rate of flow rtherein and therebyeifect rapid traverse movement of said member.

20. In a hydraulic transmission the combination of a hydraulic circuit,a casing, a variable displacement pump in said casing, means connectingsaid pump with said circuit, means for varying pump displacement, a.second pump in said casing, and adjustable means within said casing forselectively connecting said last named pump in series or in parallelwith said variable displacement pump.

2l. In a hydraulic transmission the combination of a hydraulic circuit,a casing, a variable displacement pump within said casing for feedingsaid circuit, a cam Within said casing for varying pump displacement, asecond pump, valve mechanism within said casing for controllingcommunication between said second named pump and said circuit, and meansfor controlling said cam and said valve mechanism.

22. In a hydraulic transmission the combination of a hydraulic circuit,a variable displacement pump for feeding said circuit, means forregulating pump displacement, and valve mechanism associated with saidregulating means and operable in unison therewith for automaticallyeffecting communication between the two sides of said circuit after pumpdisplacement has been reduced to zero and for closing communicationbetween the two sides of said circuit before pump displacement isincreased from zero.

23. In a hydrauliciransmission the combination of a hydraulic circuit, avariable displacement pump for feeding said circuit, means forregulating pump displacement, a second pump, valve mechanism controllingcommunication between said last named pump and said circuit, means forsimultaneously operating said regulating means and said valve mechanism,said valve mechanism having means for automatically effectingcommunication between the opposite sides of said circuit when thedisplacement of said first named pump is zero.

24. In a hydraulic transmission the combination of a hydraulic circuithaving working and return sides, and a. pump for creating pressuretherein, a second pump, valve mechanism adjustable to connect said.second pump with either the working or return side of said circuit, adischarge passage connected with the return side of said circuit in allpositions of said valve mechanism, and means for resisting the flow ofliquid through said discharge passage to mantain pressure within saidreturn side.

25. In a hydraulic transmission the combination of a hydraulic circuit,having a pump and a,

motor connected therein, a second pump, a discharge passage, valvemechanism adjustable to connect said second pump to either side of saidcircuit to drive said motor in either direction and tosimultaneouslyconnect said discharge passage with the other side of saidcircuit, and means for resisting the flow ihru said discharge passage tomaintain pressure within said other side.

26. In a hydraulic transmission the combinationof a reversible ow closedhydraulic circuit of varying volumetric capacity having interchangeableworking and return sides, a pump in said circuit for feeding the same, asecond pump, a discharge passage, means adjustable to connect saidsecond pump with either the working or return side of said circuit ineither direction of flow and-to connect said discharge passage with saidreturn side only', and means for resisting the escape of liquid throughsaid discharge passage to maintain said return side flooded with liquidunder pressure in either direction of flow.

27. The combination, with a machine tool having a movable member, of ahydraulic motor for driving said member, hydraulic pump means includinga variable displacement feed rate pump and a rapid traverse pump, liquid4conducting channels between said pump means and motor includingconnections changeable to alternatively connect said pumpsifor feed orrapid traverse movements and to reverse the direction of movement ofsaid member, and valve means operable to effect the above named changesin said channel connections, said channel connections serving tomaintain said feed rate pump iiooded regardless of the position of saidvalve means.

WALTER FERRIS.

